The conventionally-known kneading machine of both the kneading tank inversion discharging type and the sealed pressurized type is superior in economy and the like such as facility construction expenses compared with the kneading machine of the kneading tank bottom open discharging type, but has the following problems: (1) operations for discharging kneaded materials by inverting the kneading tank require time and labor; and (2) when a pressurizing lid is being closed, it is impossible to restrain jets of powder compound from a stocking opening of the kneading tank in which the inputted powder compound is accommodated.
Hereinafter, description is made on the above-mentioned problems further concretely. Firstly, as for the item (1), as shown in FIG. 7 (parts corresponding to those of an embodiment described below are denoted by the same reference symbols as the embodiment), in order to discharge the kneaded materials which are finished being kneaded in the kneading tank, generally, two kneading rotors 10 in the tank are by appropriately rotated forward and backward with a state in which a kneading tank 3 provided with the two kneading rotors 10 therein is inverted by 140 to 160° about the axis of a rotation shaft 11 of one of the kneading rotors 10 to thereby discharge the kneaded materials A from the kneading tank 3. However, when the inverting angle of the kneading tank 3 is 140 to 160°, even if an inversion direction side wall 8b of opening walls 8 surrounding four sides of a stocking opening 4 in an upper surface of the kneading tank serves as a chute, the kneaded materials A of high-polymer compounds having high viscosity have high friction, and at least considerable amount thereof does not slip down the chute, and hence an operator is compelled to conduct a discharging assist operation for raking off the kneaded materials A by a tool like a rake. In addition, such operation is extremely dangerous because this operation is a raking-off operation performed while rotating the kneading rotors. Therefore, it is strongly desired that an easy measure can eliminate necessity of man's operation. Further, an operator must move between the front and the rear of the kneading machine carrying out stocking operations and discharging operations in each batch, and this extends a batch cycle and causes loss of productivity.
In order to solve such problems, if the inverting angle of the kneading tank 3 is further increased, for example, to 180°, such a situation does not occur that the kneaded materials A contact the chute and discharging is hindered and time and labor for slipping down is required. However, high-speed and wide-range raising and inverting operations require a high-energy driving apparatus and a firm structure for a mechanism for absorbing shocks of a stop operation at the time of inversion completion caused by speed increase. Therefore, increase of inversion speed and expansion of inverting angle are limited in view of facility expenses and energy reduction. In addition, even with the above-mentioned inverting angle of 140 to 160° of the kneading tank 3, time period for inversion operations is longer than that of the kneading tank bottom open discharging type kneading machine, and therefore there is a problem in productivity.
Further, in the structure in which a surface of the stocking opening of the kneading tank 3 is inverted by 180° to discharge the kneaded materials A, the surface of the stocking opening of the inverted kneading tank 3 becomes low, and hence, it is necessary to excavate in a floor surface a space for inserting a receiving container 37 for the kneaded materials A to be discharged. If a pit is not provided by excavating the floor surface, such an arrangement is essential where the kneading machine is disposed on a base and the kneaded materials A are dropped from a high place to be discharged into the receiving container 37. However, if the kneading machine is disposed at the high place, economy in facility construction at the initial stage or at removal of facilities is deteriorated, the economy being superior in the kneading tank inversion discharging type kneading machine than that of the kneading tank bottom open discharging type. Accordingly, in the present situation, there is no choice but to introduce the inversion discharging type kneading machine which performs inversion by 140°, with holding the poor productivity of the inversion discharging type kneading machine.
The above-mentioned problem (2) is a problem that it is necessary to take measures against upward jetting of a great deal of powder compound inputted to the kneading tank 3 so as to be kneaded with respect to high-viscosity materials to be kneaded such as rubbers and plastics, with being accompanied by the air pushed out from a kneading chamber 7 by descending of a pressurizing lid 5 into the stocking opening 4, through a gap between four sides of the pressurizing lid 5 and the opening walls 8 of four sides of the kneading tank 3. That is to say, in the sealed pressurized type kneading machine, the above-mentioned jetting phenomenon of the powder compound is inevitable because the pressurizing lid 5 is rapidly pushed into the kneading chamber immediately after input of various kinds of materials into the kneading tank 3.
In order to deal with the above-mentioned problems, even if dusts from the stocking opening 4 of the kneading tank 3 is absorbed by an external dust catching machine provided in the vicinity of the stocking opening 4 to restrain diffusion of dusts, the amount of outflow from the inputted compound is uncertain. Therefore, even if the dusts captured by the dust catching machine are returned to the kneading tank 3, it is impossible to provide kneaded materials with accurate compound prescription. In addition, powder compound and the like of compound prescription in a plurality of batches get mixed in the powder compound collected by the dust catching machine, and hence, the absorbed amount and mixed rate in each compound of the caught dusts (fine particles) are also uncertain. Therefore, it is impossible to distribute and mix the caught dusts in kneading batches.
Accordingly, there is no choice but to dispose of the powder compound collected by the external dust catching machine as dusts. This situation not only generates loss of resources, but also leads to completion of kneaded materials which do not strictly follow the compound prescription as a result of partial diffusion of the powder compound. Therefore, mass-production with reproductivity of design quality is not achieved, and reliability of the quality is spoiled.